During the year progress and new findings have merged both in the chemistry of myelin in studies of myelin proteins in sciatic nerves of animals with diabetes as well as in their in vitro incorporation of precursers in myelin proteins. In the studies on rat peripheral nerve myelin protein, methods have been developed for the better resolution of polypeptide subunits in sodium dodecyl sulfate-polyacrylormide gels. The two major proteins of sciatic nerve myelin have been shown to be glycoproteins and their molecular wieights have been estimated using gels of different concentration. Previously it has been shown that there may be only one glycoprotein in sciatic nerve myelin. In rats diabetic with streptozotocin, the myelin proteins have been analyzed by the methods described above and the relative amounts of two major glycoproteins estimated by densitometric scanning of gels. The ratio of relative amounts of two major proteins in diabetic animals was 5.1 in comparison to value of 2.8 plus or minus 2 (5) for age matched controls. In vitro studies with sciatic nerves of rats made diabetic with streptozotocin incorporation in DL-Leucine (1-C14) into myelin was 30 to 60% of age matched controls. Analysis of radioactivity indicated that the major protein was poorly labelled while the peptides present in lower amounts had main radioactivity.